Roussin's Red Salt

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Roussin's Red Salt
IUPAC name potassium tetranitrosyl-di-μ-sulfidodiiron(Fe–Fe)(2–)
Other names Ferrate(2-), tetranitrosyldi-mu-thioxodi-, (Fe-Fe), dipotassium
Identifiers
CAS number [58204-17-4]
Properties
Molecular formula Fe2N4K2O4S2
Molar mass 374.04 g/mol
Appearance Dark red crystals
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Roussin’s Red Salt is the inorganic compound with the formula K2][Fe2S2(NO)4]. This metal nitrosyl consists of the potassium salt of the [Fe2N4O4S2]2− anion. This compound was first described in 1858 by the French chemist M.L. Roussin while experimenting with reactions between nitroprusside ion, [Fe(CN)5NO]2−, and sulfur, making it the first synthetic iron-sulfur cluster.[1]

Contents

[edit] Structure and bonding

Roussin's red salt anion is an example of a ligand-bridged metal dimer. Its structure is described as an edge-shared bitetrahedron, wherein a pair Fe(NO)2 units are bridged by a pair of sulfide ligands. The Fe-NO bonds are linear indicating NO is acting as a three electron donor.[2] The diamagnetic compound obeys the 18-electron rule, and each iron center is assigned the oxidation state of Fe(-I).

It is found in nature as its “esters" with the formula Fe2(SR)2(NO)4, where "R" is any alkyl group [1]. In addition Roussin’s red salt is discussed in the fields of microbiology and food science due to its mutagenic properties.[3]

[edit] Synthesis

The Roussin’s red salt can be prepared by the reaction of sulfide salts with iron nitrosyl halides:[4]

Fe2I2(NO)4 + 2Li2S → Li2Fe2S2(NO)4 + 2LiI

To obtain the esters, the salt is alkylated:

Li2Fe2S2(NO)4 + 2 RX → Fe2(SR)2(NO)4 + 2 LiX

Esters can also be easily be prepared from the reaction of Fe2I2(NO)4 with the thiol.

[edit] Potential applications

Today one common use of Roussin's red salt is of the ester derivative. This class of compounds is being investigated as a nitric oxide donor in biology and medicine. Due to its relatively low toxicity and good stability Roussin’s red salt can act as a possible chemotherapeutic. Photolysis of the compound induces the release of NO, thereby sensitizing target cells to exposure to radiation [2].

[edit] See also

Roussin's black salt

[edit] References

  1. ^ Roussin, M. L. (1858). "Recherches sur les nitrosulfures doubles de fer (nouvelle classe de sels)". Ann. Chim. Phys. 52: 285 - 303. 
  2. ^ Thomas, J., Robertson, J., & Cox E. (1958). The Crystal Structure of Roussin’s Red Ethyl Ester. Acta Crystallographica, 11, 599.
  3. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  4. ^ TB Rauchfuss, TD Weatherill (1982). "Roussin's Red Salt revisited: reactivity of Fe2 (. mu.-E) 2 (NO) 42-(E= S, Se, Te) and related". Inorganic Chemistry 21: 827-830. 

See also